My 89-year-old father suffers from constant dizziness and recently fainted while getting out of the car. He takes a beta-blocker for his heart but is otherwise healthy. Any idea what the cause might be? —M.S., Pukalani, Hawaii

His medication could be the culprit. Blood-pressure drugs can sometimes reduce the pressure so much that insufficient blood gets to the brain—a prime cause of dizziness as well fainting when a person stands up. More commonly, though, blood flow to the brain is reduced by abnormal heart rhythms, arterial blockage around the brain, and transient ischemic attacks, or minor strokes. Dehydration or blood vessels that fail to adjust properly to standing can also cause fainting. Tests to pinpoint the culprit may include a tilt-table, which measures blood pressure and heart rhythms as you’re slowly moved from a lying position to a standing one. Your father should ask his doctor about having such a test.